Microarrays offer great potential for performing complex analyses of samples by carrying out multiple detection reactions simultaneously. Typically, a microarray of multiple spots of reactant molecules is formed on a planar substrate such as a glass microscope slide, usually in a two-dimensional grid pattern. Liquid sample and reagents are then applied to the slide to contact multiple spots simultaneously. Various reaction steps may be performed with the bound molecules in the microarray, including exposure of bound reactant molecules to the liquid sample and reagents and washing steps. The progress or outcome of the reaction may be monitored at each spot in the microarray in order to characterize either material(s) immobilized on the slide or material(s) in a liquid sample.
Microarray analysis usually requires an incubation period that ranges from minutes to hours. The duration of the incubation period is assay dependent and is determined by a variety of factors, such as the type of reactant, degree of mixing, sample volume, target copy number, and density of the array. During the incubation period, target molecules in the liquid sample must be in intimate contact with the microarray probes. The incubation is usually performed in an incubation chamber. The incubation chamber is typically formed by forming a gasket around the microarray. The gasket is covered with a cover slip to form an enclosed chamber. The cover slip can be made of a transparent material, such as glass, to allow optical interrogation of the microarray after the incubation.
If the cover slip does not have an entry port and a vent, the liquid sample and other reagents need to be added to the incubation chamber before the cover slip is placed on top of the gasket. If the reaction mixture is filled to the rim of the gasket, the reaction mixture may leak out of the side of the gasket, compromising the gasket/cover seal and increasing the risk of contaminating the environment. Cover slips with holes for filling and venting circumvent these two problems. However, filling the incubation chamber through holes on the cover slip often risks the introduction of air bubbles or air pockets into the incubation chamber. Moreover, surface tension of a liquid sample or a reaction mixture may also prevent the liquid sample or reaction mixture from completely filling the incubation chamber. A partially filled chamber may result in a false negative if an air pocket covers an array spot and prevents contact between the array spot and the liquid sample or reaction mixture.